EBNA IgG is a marker that reflects the presence of antibodies against the EBV (Epstein-Barr virus) nuclear antigen (EBNA), a protein produced during the later stages of infection. The presence of EBNA IgG antibodies generally indicates a past infection, as these antibodies develop several weeks to months after the initial infection and typically remain detectable for life. Testing for EBNA IgG is often used alongside VCA antibodies to differentiate between a current and past infection and to assess the stage of the infection.